The present invention is related to data transmission over power lines, in general, and more particularly, to the data transmission over a power line of a switch mode power supply (SMPS) by frequency modulating the switch frequency thereof.
In existing systems for data transmission over a power line, the information or data signal is encoded by amplitude modulation (AM) or frequency modulation (FM), and then, coupled onto the power line at the transmitting end via a power line coupling network including capacitors and/or transformers, for example. At the receiving end of the power line, capacitors or transformers couple the encoded data signal from the power line to a decoding network to extract the transmitted data. An example of such an existing system is disclosed in the U.S. Pat. No. 5,717,685, entitled “Transformer Coupler for Communication Over Various Lines”, patented Feb. 10, 1998 to Charles Abraham. Note that, with all such systems, coupling capacitors or transformers are needed at both the transmitting end and receiving ends of the power line. Also, with these existing systems, reflected impedances must be considered as they may load the encoder/decoder circuitry. In such existing systems, the encoded data signal creates an undesirable ripple voltage frequency over the power line. The present invention intends to overcome these drawbacks of the existing systems.